Manufacture of artificial threads, films, and other products by wet spinning processes from solutions of cellulose esters or ethers



Dec. 31 1935. w D KE ETAL 2,025,730

MANUFACTURE OF ARTIFICIAL THREADS, FILMS AND OTHER PRODUCTS BY WET SPINNINGPROCESSES FROM SOLUTIONS OF GELLULOSE ESTERS OR ETHERS Filed Jan. 28, 1932 j F'IG-2- Patented Dec. 31, 1935 UNITED STATES ATENT OFFICE MANUFACTURE OF ARTIFICIAL THREADS, FILMS, AND OTHER PRODUCTS BY WET SPINNING PROCESSES FROM SOLUTIONS OF CELLULOSE ESTERS OR ETHERS Application January 28, 1932, Serial No. 589,428 In Great Britain March 27, 1931 2 Claims.

This invention, which is a continuation in part of the invention described in application S. No. 402,785 filed October 26, 1929, relates to the manufacture of artificial filaments, yarns, threads, ribbons, films or other products by .wet spinning processes from solutions of cellulose esters or ethers, and particularly solutions of cellulose acetate.

In U. S. Patents Nos. 1,465,994 and 1,467,493 processes are described for the manufacture of artificial filaments or threads by wet spinning processes in which solvents or latent solvents for the cellulose derivative of the spinning solution are incorporated in the coagulating bath, so as to enable the products to be drawn out to fine deniers and also to increase the stability of spinning. Further, in U. S. application S. No. 402,785 filed 26th October, 1929 there are described processes in which the coagulation of the cellulose derivative is eifected in presence of concentrated solvents for the cellulose derivative, such solvents being present in the coagulating bath and/or introduced therein from the spinning solution, and also processes wherein the filaments, threads or other products immediately after coagulation are carried into a medium in which they are subjected to the action of relatively concentrated solvents so as to bring them to a plastic state. Again, U. S. application S. No. 418,414 filed 3rd January, 1930 effects coagulation in a bath containing plasticizing agents for the cellulose derivative, such as tricresyl phosphate, diethyl phthalate or sulphonamides, or the filaments or threads or other products immediately after coagulation are treated with such plasticizing agents, the plasticizing agents being employed alone or mixed with solvents and/or non-solvents for the cellulose derivative. In these last two specifications the concentration of the solvent or plasticizing agent present in the coagulating medium or in the subsequent treatment medium may be such that the products on emergence therefrom are in a plastic state, while in the processes described above by way of example in U. S. Patents Nos. 1,465,994 and 1,467,493 the products pass through the plastic state which persists more or less during their passage through the coagulating medium.

The present invention relates to methods for obtaining filaments, threads or other products of improved properties, and particularly of improved tenacity, by wet spinning processes in which the filaments, threads or other products during coagulation or subsequent treatment pass through the plastic state and preferably in wh ch such plastic state persists for a considerable periocl.

All the specifications referred to above describe drawing out the products to fine deniers or products oflow cross-section. We have now found that products of increased tenacity may be produced by spinning according to any of the said prior processes and applying a tension to the filaments in such a manner that little or none is exerted upon the products immediately upon their exit from the spinning jets, and that the main pull is applied after coagulation but while the products are in a plastic state. Thus in any of the processes of U. S. applications S. Nos.

402,785 and 418,414 a stretch or an additional 15 stretch may be applied to the filaments or other products after they have become plastic. As is indicated in the said specifications the products obtained by using very high concentrations of solvents or plasticizing agents are still plastic when they leave the coagulating or subsequent treatment medium, so that once they have acquired this plasticity, the stretch according to the present invention or the additional stretch may be applied at any convenient point. Viewed from another aspect, the present invention may be said to consist in effecting coagulation or subsequent treatment under such conditions that plasticity of the filaments or products occurs and preferably persists for some time, and stretching or subjecting the products to tension and so restricting the action of the said stretch or tension that it does not run back or does not wholly run back to the spinning nozzle.

The stretch or tension may be restricted to the plastic portion of the filaments or other products by any suitable means, as for example by carrying the filaments or other products round or otherwise in contact with suitable guides, gates, godets or other devices adapted to prevent the whole of the stretch being effective from the spinning nozzle itself. If desired instead of employing purely mechanical means to restrict the tension or stretch, the coagulating bath or subsequent treatment bath may move in a direction counter to that of the filaments or other products so as to exert a tension thereon in the reverse direction to that applied to the running filaments, thereby restricting the whole or part of the tension or stretch to the plastic portion of the filaments.

As in the various prior specifications referred to, the invention is of greatest importance in $1 manufacture of filaments, threads, yarns, ribbons, films or other products of cellulose acetate or of other organic derivatives of cellulose, for example cellulose formate, propionate or butyrate, or methyl, ethyl or benzyl cellulose, but it may also be applied to the manufacture of products from other cellulose derivatives, for example nitro cellulose.

Among suitable solvents for making up the spinning solution may be mentioned acetone, acetic acid, and mixtures of ethylene or methylene dichloride with ethyl or methyl alcohol, while the spinning solution may also contain relatively high boiling solvents, for example diacetone alcohol, ethyl lactate, and diethyl tartrate.

The percentage of cellulose derivative in the spinning solution may vary within wide limits, but in general solutions containing from 15-30%, and preferably about 25%, have been found suitable.

Spinning may be carried out at normal temperatures, or at temperatures above or below normal. tures above normal, e. g. at 40-60 C., the stretching process is facilitated, and products of low denier may be obtained, as described in prior U. S. application S. No. 316,617 filed 1st November, 1928.

As already indicated, the new process may be carried into effect using any of the processes described in U. S. Patents Nos. 1,465,994 and 1,467,493 and U. S. applications S. Nos. 402,785 and 418,414. For example a coagulating bath or subsequent treatment bath may be used consisting of aqueous or alcoholic diacetone alcohol, diethyl tartrate, ethyl lactate, lactic acid, dioxane and the like in a concentration of 25 to 65% strength. Further, a coagulating or subsequent treatment medium may be used consisting of tricresyl phosphate or diethyl phthalate in a concentration of 60 to the remaining medium being a solvent, such as acetone, or a non-solvent for the cellulose derivative. Furthermore the coagulating baths or subsequent treatment baths may contain salts or sugars or other substances capable of exerting an osmotic pressure or of decreasing the solubility of the solvent of the coagulating bath in the non-solvent medium thereof, as described in U. S. application S. No. 469,622 filed 21st July, 1930.

Any other suitable coagulating medium may be employed, provided that the coagulation is so effected that the filaments or other products pass through a plastic state, and preferably so that they retain the plastic state for a considerable period of time or sufficient to enable the stretch to be applied. Thus, for example, the filaments or other products may be coagulated in monohydric or polyhydric alcohols, e. g. methyl or ethyl alcohol, or even in hydrocarbons, (preferably containing solvents for the cellulose derivative) or oils, for example castor oil, olein etc.

In the case of employing the movement of the coagulating bath or subsequent treatment bath itself to restrict the stretch or tension, the said medium should preferably be of high viscosity, the high viscosity being achieved, for example, by addition of suitable agents, such as colloids or sugars and carbohydrates in general and other polyhydric alcohols, to the coagulating or subsequent treatment medium. The concentration of such sugars, for example, may be higher than that indicated in U. S. application S. No. 469,622, since the medium is to exert a drag upon the filaments or other products.

Various types of apparatus which may be When spinning is carried out at temperaployed according to the invention are shown in the accompanying drawing, but it is to be clearly understood that they are given by way of illustration only and the invention is in no way limited thereto.

Fig. 1 shows a form of wet spinning apparatus in which a bundle of filaments 6 is extruded from a spinning jet 1 into a suitable bath contained in a vessel 8. The bundle of filaments is passed round a draw roller 9 which subjects them to tension, and in order that application of the stretching force may be wholly or partially limited to the filaments after they are more or less coagulated and are still in a plastic condition, and that the full tension may be prevented from going back to the spinning jet, the filaments are passed through a wire or glass grid 10 interposed between the spinning jet and the draw roller.

Fig. 2 shows a similar apparatus in which a bundle of filaments 6 is extruded from a spinning jet 1 into a coagulating bath contained in the vessel 8, and are stretched by means of a draw roller 9, but in this case the portion of the filaments to which the full tension is applied is lim- 'ited by passing them round a small pulley l l A further form of apparatus is shown in Fig. 3, in which a bundle of filaments 6 is extruded from the spinning jet 1 into a coagulating bath contained in the vessel 8, and are then passed under a guide M and round two stretching rollers 12 and IS, the roller l3 having a greater peripheral.

velocity than the roller 12 in order that stretch may be applied to the filaments during their pas-,

sage between the two rollers. The roller I 2 is preferably rotated at such a speed that little or no tension is applied to the filaments on issuing from the spinning jet 1.

In another form of apparatus shown in Fig. 4, the bundle of filaments 6 extruded from the spinning jet 1 is coagulated in a suitable bath contained in the vessel 8, and then passed under a guide l4 and over or round a series of rollers Hi, the peripheral velocities of the rollers increasing successively so that a stretch is applied to the filaments during their passage round the said rollers. In order that the filaments may remain in a plastic state throughout the stretching operation they are passed through a secondary bath 16.

Still another means of restricting the tension applied to the filaments is shown in Fig. 5, which illustrates a form of apparatus in which the bundle of filaments 6 extruded from the spinning jet 1 and coagulated in the vessel 8 is passed through a fork-tension device I! and thence round the stretching roller 9. By varying the angle of inclination of the fork I! the ratio of the tensions applied to the filaments before and after passage through the fork may be varied as desired. r

A suitable coagulating bath for use with any of the above forms of apparatus consists of a 40-50% aqueous solution of diacetone alcohol or ethyl lactate, the length of immersion being about ample .a 55% aqueous solution of diacetone alcohol.

Alternatively the apparatus described above may be modified so that the products after coagulation are passed through subsequent treatment baths in which they are brought to a plastic state, e. g. an} of the baths described in U. S. application S. No. 402,785, the stretch being applied during or subsequent to this process.

After passage over the stretching rollers the filaments or other products may be collected on swifts, bobbins, in spinning boxes or in any other suitable manner.

What we claim and desire to secure by Letters Patent is:

1. Process for the manufacture of artificial filaments, threads, ribbons, films and similar products, which comprises extruding a solution containing cellulose acetate through suitable orifices into a coagulating bath containing relatively high proportions of a compound selected from the group consisting of solvents and plasticizers and. subjecting the products directly to a stretching operation whilstthey are in a plastic state, only a portion at most of the stretching force employed being allowed to act on the filaments or other products immediately upon extrusion.

2. Process for the manufacture of artificial filaments, threads, ribbons, films and similar products, which comprises extruding a solution containing an organic derivative of cellulose through suitable orifices into a coagulating bath containing relatively high proportions of a compound selected from the group consisting of solvents and plasticizers and subjecting the products directly to a stretching operation whilst they are in a plastic state, only a portion at most of the stretching force employed being allowed to act on the filaments or other products immediately upon extrusion.

WILLIAM ALEXANDER DICKIE. PERCY FREDERICK COMBE SOWT'ER. 

